The present invention relates to a new and improved machine tool, and more specifically to an improved chuck actuator assembly.
Many machine tools, such as the machine tool disclosed in U.S. Pat. No. 3,835,516 to Fullerton include a chuck which is utilizied to grip and rotate a workpiece. A hydraulic motor is commonly provided to open and close the chuck. During operation of the machine tool, the chuck jaws are held closed under the influence of high-pressure fluid in the motor.
If the conduit which supplies high-pressure fluid to the motor is accidentally broken during operation of the machine tool of if the power for driving the pump to supply the fluid pressure to the motor is interrupted, the exhausting of fluid from the motor chamber could cause the chuck to lose its grip on the workpiece. Of course if the workpiece is rotating at a relatively high speed, this could result in a serious accident. In order to prevent the exhausting of fluid from the motor chamber upon accidental rupturing of the fluid supply conduit during operation of the machine tool, check valves have been associated with the supply conduits for the motor chamber in a manner similar to that disclosed in U.S. Pat. Nos. 3,364,823; 3,411,415; and 3,596,567. Although these known check valve arrangements have been more or less successful in their mode of operation, difficulty may be encountered due to the loss of a relatively small quantity of fluid from the motor chamber of the chuck actuator assembly upon closing of the check valve. This loss of even a relatively small quantity of fluid from the motor chamber could result in a tendency for the chuck to relax its grip on the workpiece.